The present application relates to the examination of pipelines or other fluid transport vessels (e.g., pipeline section, column, heat exchanger silo, etc.) using radiation. It finds particular application to the use of ionizing radiation in aboveground oil pipeline inspections. It also relates to other applications where data from a movable scanner may be used to provide information about the structure and/or dynamics of an object being scanned.
Radiation, in general, penetrates an object under examination. The object is exposed to radiation, and information is acquired based upon the radiation absorbed by the object, or rather an amount of radiation that is able to pass through the object. Typically, highly dense objects absorb more radiation than less dense objects. For example, a thick metal plate may absorb more radiation than a thin metal plate, and thus information related to various properties of the plates (e.g., thickness, composition, etc.) may be acquired based upon the radiation that is absorbed.
Radiation devices commonly comprise a radiation source and a detector array. The radiation source and detector array are typically positioned on substantially diametrically opposing sides of the object under examination. Radiation, emitted from the radiation source, interacts with the object under examination. Radiation that traverses the object is detected by the detector array. Data, produced based upon the detected radiation, may then be used to determine characteristics of the object under examination and/or used to produce an image of the object.
Inspection of pipelines is common to detect defects, obstructions, and other flaws in the manufacturing process that may affect the flow of a fluid. Additionally, over time pipelines may endure abrasion, corrosion, etc. that may lead to structural fatigue, divots, or cracks that cause the pipeline to leak or otherwise affect performance. Leakage of a fluid may lead to substantial monetary cost and production delays for the entity responsible for the pipeline, so the sooner defects, cracks, wall thinning, etc. can be detected, the better.
Radiation is utilized in the inspection process to measure characteristics of a pipeline that are unable to be visually inspected. For example, radiation provides a mechanism for measuring the thickness of a pipeline's wall. While other mechanisms for measuring similar characteristics have been devised, radiation works particularly well for some applications because results are minimally affected by properties of the pipeline that are not being measured, such as an insulation layer covering an external surface of the pipeline's wall, for example. Additionally, unlike some other mechanisms that measure characteristics from within the pipeline (e.g., a “pig”), radiation devices may measure the characteristics from locations external to the pipeline.
One type of radiation inspection device used to inspect pipelines is disclosed in U.S. Pat. No. 5,698,854 to Gupta. Gupta describes a carriage configured to be moveably mounted to a pipeline and to circumferentially enclose a scanning portion of the pipeline. As the carriage slowly moves axially along a portion of the pipeline, a radiation source emits radiation that may be detected by a detector array.
Another type of radiation inspection device used to inspect pipelines is disclosed in U.S. Pat. No. 6,925,145 to Batzinger et al. Batzinger et al. describe a controller that causes a scanner to move along a pipeline. In one embodiment, a radiation source and a detector array that are part of the scanner are connected to an arcuate bracket that allows the radiation source and detector array to be rotated while moving along the pipeline. However, the Batzinger et al. device is deficient at least in that it does not allow the scanner to inspect a portion of the pipeline adjacent to, or rather touching, a pipe support.
While current radiation devices have proven useful in some inspection applications, there remains room for improvement. Obstructions (e.g., beams, marking posts), directional changes in the pipeline, etc. prevent current radiation inspection devices from collecting data related to portions of the pipeline that are in close proximity to the obstruction, such as portions touching and/or nearby the obstruction. Obstructions also make it difficult and/or impossible for some radiation inspection devices to travel past the obstruction and continue scanning without the device being disconnected from the pipe and then reassembled on the other side of the obstruction. Some radiation inspection devices are also not configured to rotate in a transverse, or rather radial, direction with respect to the pipeline, making it more difficult to acquire accurate and/or reliable data for various portions of the pipeline. Additionally, some of the radiation inspection devices require significant human intervention (e.g., piloting the device as it moves axially along the pipeline) which may make operation of a device very costly. The slow speed at which some radiation inspection devices move axially along a pipeline also poses a problem in some applications because it takes too long to scan a meaningful length (e.g., thousands of miles) of the pipeline.